It depends on the fish, I think. Touchstone won't flare at all. Ares flares at the tank walls to the point of tail biting. Freyja flares at many things(mirrors,nail polish, the camera, and people if they get too close to her bubble nest!) Touchstone doesn't flare or make bubble nests and I have had him for over 2 years. If the water conditions are fine and he is active, I wouldn't worry too much.
Ares - My flare happy warrior
Castiel - My inquisitive crowntail
Sammie,Jackie, and Jamie - My fun loving peppered cories.
Touchstone - My sweet fool
Freyja - My beautiful girl